My live setup is: guitar going through some pedals into a stereo looper pedal. Mic going into preamp into the other channel of the looper pedal.

There are a few moment when I want my mic to go through the guitar pedals. And I was trying to figure out a way to do this with an AB type pedal, but it's more complicated than that. The mic would have to merge with the guitar signal.

I figured the easiest way would be to get a pedal that has A/B in and A/B out. In its normal state, A goes to A, B goes to B. But when I click it, A goes to B, and B goes to A. That way the guitar will continue into the looper, and the mic will go through the pedals.

I can't find any pedal that can do such a thing. In a way it's a stereo inverter, L goes to R, R to L. But that doesn't seem to exist either in pedal form.

I might be overlooking an easier way to do this, so any advice is appreciated. Thanks

The levels would be different going into the pedals, because you have line level from the mic and instrument from your guitar, which would cause problems with OD pedals and such. And is your preamp's output balanced or unbalanced?
Have you ever soldered/do you want to build something?
I dont think there is a commercial offering that does this kind of switching.

*Edit - wouldn't cause problems, but would change gain in an overdrive, for example. A line output could also be too high for certain choruses/delays or other effects, and cause clipping.

The output of the preamp should be OK with the pedals, why not just let the vocals mix with the guitar when you want to loop them? Much easier: guitar to pedals, mic to preamp to AB box with one side leading to pedals and other to looper. To mix the guitar and vocal levels you can use a simple DOD resistance mixer-less than $50!

To get the ABXAB pedal built, talk to Jack DeVille. He builds clickless relays, you'd have one relay take care of switching the guitar to A or B output and another control the vocal output...

This can definitely be done, I built a box called the "Mic-Line Patch" years ago that could be patched inline with your microphone and let it go feed out to effects.

The real question is, how good do you want the final thing to sound? Besides relays you need some transformers to take the low impedance balanced mic output and convert it to single-ended to drive the effects pedals. It's an impedance matching step, then you need relays to keep the systems separate, you can't go mixing grounds or you'll have buzz for days and wonder why.

To do this right it will require some drilling of metal boxes, acquiring the parts and building it. It's not a rocket science build but it's a lot of fabrication.

Relays are the only way to switch as many contacts as you're talking about and keeping all the grounds correct.

PM me if you want design help, I'm in the process of setting up a new shop in California and can't do the build personally right now but I could certainly point you at some parts and help with the design if you want.